Methods for etch mask and fin structure formation

ABSTRACT

Embodiments described herein relate to substrate processing methods. The methods include forming a patterned hardmask material on a substrate, forming first mandrel structures on exposed regions of the substrate, and depositing a gap fill material on the substrate over the hardmask material and the first mandrel structures. The first mandrel structures are removed to form second mandrel structures comprising the hardmask material and the gap fill material and the substrate is etched using the second mandrel structures as a mask to form fin structures.

BACKGROUND Field

Embodiments of the present disclosure generally relate to methods for etch mask and fin structure formation.

Description of the Related Art

Fin field effect transistors (FinFETs) are structures commonly utilized in the fabrication of semiconductor devices. Conventional FinFETs at current technology nodes are fabricated with conventional etching techniques. However, at advanced technology nodes with reduced critical dimensions and increasing aspect ratios, conventional etching techniques are inadequate to fabricate defect free FinFET devices.

For example, in order to fabricate FinFET devices with sufficient verticality for utilization in various semiconductor devices, thick spacers are utilized to pattern an underlying hardmask. The thick spacer height is utilized to reduce bending or leaning of the patterned spacer. However, when the spacer pattern is transferred to the hardmask, less than desirable verticality of the hardmask may persist which results in FinFET devices with slanted sidewalls or occluded trenches between adjacent FinFET structures.

Thus, what is needed in the art are improved methods for mask and fin structure fabrication and etching.

SUMMARY

In one embodiment, a substrate processing method is provided. The method includes forming a patterned hardmask material on a substrate, forming first mandrel structures on regions of the substrate exposed between the patterned hardmask material, and depositing gap fill material on the substrate over the hardmask material and the first mandrel structures. The method also includes removing the first mandrel structure to form second mandrel structures comprising the hardmask material and the gap fill material and etching the substrate using the second mandrel structures as a mask to form fin structures.

In another embodiment, a substrate processing method is provided. The method includes forming a hardmask material on a substrate, depositing a spacer material on the hardmask material, patterning the spacer material, and transferring the pattern of the spacer material to the hardmask material by etching the hardmask material to expose regions of the substrate. First mandrel structures are formed on the exposed regions of the substrate. A gap fill material is deposited on the substrate over the hardmask material and the first mandrel structures. The first mandrel structures are removed to form second mandrel structures comprising the hardmask material and the gap fill material. The substrate is etched using the second mandrel structures as a mask to form fin structures.

In yet another embodiment, a substrate processing method is provided. The method includes forming a patterned hardmask material on a substrate and forming III-V material first mandrel structures on exposed region of the substrate. The III-V material first mandrel structures extend a first distance of greater than about 80 nm above a top surface of the substrate. A flowable oxide gap fill material is deposited on the substrate over the hardmask material and the III-V material first mandrel structures. The III-V material first mandrel structures are removed to form second mandrel structures comprising the hardmask material and the flowable oxide gap fill material. The second mandrel structures extend a second distance above the top surface of the substrate approximately equal to the first distance. The substrate is etched using the second mandrel structures as a mask to form silicon containing fin structures, and subsequently the second mandrel structures are removed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.

FIG. 1 illustrates a partial cross-sectional view of a substrate having a patterned spacer material and hardmask material formed thereon according to an embodiment described herein.

FIG. 2 illustrates a partial cross-sectional view of the substrate of FIG. 1 with the spacer material removed and first mandrel structures formed on the substrate according to an embodiment described herein.

FIG. 3 illustrates a partial cross-sectional view of the substrate of FIG. 2 with a gap fill material formed on the substrate over the hardmask material and the first mandrel structures according to an embodiment described herein.

FIG. 4 illustrates a partial cross-sectional view of the substrate of FIG. 3 after planarization of the gap fill material according to an embodiment described herein.

FIG. 5 illustrates a partial cross-sectional view of the substrate of FIG. 4 with the first mandrel structures removed to form second mandrel structures according to an embodiment described herein.

FIG. 6 illustrates a partial cross-sectional view of the substrate of FIG. 5 after etching of the substrate according to an embodiment described herein.

FIG. 7 illustrates operations of a method for patterning and etching a substrate according to an embodiment described herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments described herein relate to substrate processing methods that are particularly suitable for forming fin structures. The methods include forming a patterned hardmask material on a substrate, forming first mandrel structures on exposed regions of the substrate, and depositing a gap fill material on the substrate over the hardmask material and the first mandrel structures. The first mandrel structures are removed to form second mandrel structures comprising the hardmask material and the gap fill material and the substrate is etched using the second mandrel structures as a mask to form fin structures. Utilization of the embodiments described herein enables efficient fabrication of etch masks with improved thicknesses and verticality profiles which are utilized to subsequently form advanced node fin structures.

FIG. 7 illustrates operations of a method 700 for patterning and etching a substrate according to an embodiment described herein. The method 700 is discussed concurrently with the illustrations depicted in FIGS. 1-6. At operation 710, a spacer material is patterned and the pattern is transferred to an underlying hardmask material.

FIG. 1 illustrates a partial cross-sectional view of a substrate 102 having a patterned spacer material 106 and a hardmask material 104 formed thereon according to an embodiment described herein. In one embodiment, the substrate 102 is fabricated from a semiconducting material, such as silicon. For example, the substrate 102 is a monocrystalline silicon material which is either an intrinsic (un-doped) silicon material or an extrinsic (doped) silicon material. If an extrinsic silicon material is utilized, the dopant may be a p-type dopant, such as boron. In another embodiment, the substrate 102 is a silicon-on-insulator substrate.

FIG. 1 illustrates the spacer material 106 and the hardmask material 104 after patterning at operation 710. Prior to patterning, the hardmask material 104 is deposited on and in contact with the substrate 102 in a blanket type layer. The spacer material 106 is then deposited on and in contact with the hardmask material 104. Patterning of the spacer material 106 is performed by various processes suitable for advanced technology nodes, such as the 10 nm node, the 7 nm node, the 5 nm node, and beyond. Examples of suitable patterning processes include self-aligned double patterning and self-aligned quadruple patterning which are, depending upon the desired implementation, immersion lithography or extreme ultraviolet (EUV) lithography processes. Other suitable patterning processes include directed self-assembly, 193 nm immersion litho-etch-litho-etch (LELE), and EUV LELE, among others.

The patterned spacer material 106 creates a mask for subsequent etching of the underlying hardmask material 104. In one embodiment, the spacer material 106 is a silicon oxide material, a silicon nitride material, or a titanium oxide material. In one embodiment, a thickness of the patterned spacer material 106 is approximately equal to one half of the fin pitch. For example, the thickness of the patterned spacer material is between about 15 nm and about 20 nm. In one embodiment, a thickness of the hardmask material 104 is between about 30 nm and about 50 nm, such as about 40 nm. The hardmask material 104 is fabricated from a silicon oxide material in one embodiment and a silicon nitride material in another embodiment.

An etching process, such as a wet etching process or dry etching process, is utilized to etch the hardmask material 104, thus transferring the pattern from the spacer material 106 to the hardmask material. In one embodiment, a fluorine based etchant is utilized to etch one or both of the spacer material 106 and/or the hardmask material 104. For example, the hardmask material 104 is etched by a capacitively coupled fluorine containing plasma. In another example, the hardmask material 104 is etched by an inductively coupled fluorine containing plasma. Examples of suitable plasma precursors include fluorocarbon or hydrofluorocarbon materials, such as C₄F₆, C₄F₈, CF₄, CH₂F₂, and CH₃F. A source power utilized to generate the plasma is between about 300 W and about 1500 W, a bias power utilized to bias the plasma is between about 50 W and about 700 W, a pressure of a process environment for performing the etching process is maintained between about 5 mTorr and about 20 mTorr, and a temperature of the substrate 102 during the etching process is maintained between about 10° C. and about 80° C. After etching of the hardmask material 104, regions 114 of the substrate 102 are exposed between adjacent portions of the hardmask material 104.

A pitch 108 of the patterned hardmask 106 is less than about 40 nm, such as about 30 nm or less. In this embodiment, a width 110 of patterned hardmask material portions is about 20 nm or less, such as about 15 nm or less. Similarly, a width 112 of the exposed regions 114 is about 20 nm or less, such as about 15 nm or less.

FIG. 2 illustrates a partial cross-sectional view of the substrate of FIG. 1 with the spacer material 106 removed and first mandrel structures 202 formed on the substrate 102 according to an embodiment described herein. At operation 720, first mandrel structures 202 are formed on a substrate patterned by the hardmask material 104 as shown in FIG. 2. The spacer material 106 is removed by suitable selective etching processes, such as a wet etching process or a dry etching processes.

In embodiments where the spacer material 106 is a silicon oxide material, a plasma is generated from one or more of the following precursors: C₄F₆, O₂, Ar, and He. In this embodiment, a source power utilized to generate the plasma is between about 300 W and about 900 W, a bias power utilized to bias the plasma is between about 300 W and about 700 W, and a pressure of a process environment for performing the etching process is maintained between about 5 mTorr and about 15 mTorr. In embodiments where the spacer material 106 is a silicon nitride material, a plasma is generated from one or more of the following precursors: CH₃F, CH₄, O₂, H₂, N₂, and He. In this embodiment, a source power utilized to generate the plasma is between about 400 W and about 800 W and a bias power utilized to bias the plasma is between about 30 W and about 100 W. In other embodiments where the spacer material 106 is a silicon oxide material, a dilute HF wet etching process is utilized.

In one embodiment, suitable apparatus for performing the etching process is the CENTRIS™ SYM3™ etching apparatus available from Applied Materials, Inc., Santa Clara, Calif. It is contemplated that other suitably configured apparatus from other manufacturers may also be utilized in accordance with the embodiments described herein. The spacer removal process removes the spacer material 106 selectively to the hardmask material 104 and the substrate 102, leaving the hardmask material 104 on the substrate 102.

The first mandrel structures 202 are formed in the exposed regions 114 depicted in FIG. 1. The first mandrel structures 202 are deposited on a surface 206 of the substrate 102 and the first mandrel structures 202 are grown from the surface 206 of the substrate 102. In one embodiment, a suitable apparatus for performing the first mandrel structure deposition is the CENTURA® RP EPI apparatus available from Applied Materials, Inc., Santa Clara, Calif. It is contemplated that other suitably configured apparatus from other manufacturers may also be utilized in accordance with the embodiments described herein. Each of the first mandrel structures 202 are separated from adjacent first mandrel structures 202 by the patterned hardmask material 104 and voids 210. The first mandrel structures 202 are grown such that a top surface 208 of the first mandrel structures 202 is a distance 204 that is greater than about 80 nm above the surface 206 of the substrate 102. In one embodiment, the distance 204 is between about 100 nm and about 200 nm.

In one embodiment, the first mandrel structures 202 are formed on the substrate 102 using an epitaxial deposition process. In one embodiment, a gallium containing precursor and an arsenic containing precursor are pulsed in an alternating matter to deposit the first mandrel structures 202. In this embodiment, the gallium containing precursor is trimethylgallium and the arsenic containing precursor is AsH₃. In this embodiment, the first mandrel structures 202 are fabricated in an environment maintained at a pressure of between about 1 torr and about 10 Torr and a temperature of between about 450° C. and about 800° C. The epitaxial deposition process utilizes a layer-by-layer deposition technique which is believed to maintain the substantially vertical orientation of the first mandrel structures 202 as the first mandrel structures 202 continue to grow from the surface 206 and above the hardmask material 104.

In one embodiment, the first mandrel structures 202 are formed from a III-V material. For example, the first mandrel structures 202 are formed from one or more of aluminum antimonide, aluminum arsenide, aluminum gallium arsenide, aluminum gallium indium phosphide, aluminum gallium nitride, aluminum gallium phosphide, aluminum indium arsenide, aluminum nitride, aluminum phosphide, boron arsenide, boron nitride, boron phosphide, gallium antimonide, gallium arsenide, gallium arsenide phosphide, gallium phosphide, indium antimonide, indium arsenide, indium gallium arsenide, indium gallium nitride, indium gallium phosphide, indium nitride, and indium phosphide, among others.

At operation 730, the gap fill material 302 is deposited on the substrate 102 over the hardmask material 104 and the first mandrel structures 202. FIG. 3 illustrates a partial cross-sectional view of the substrate 102 of FIG. 2 with a gap fill material 302 formed on the substrate 102 over the hardmask material 104 and the first mandrel structures 202 according to an embodiment described herein. The gap fill material 302 is deposited such that the gap fill material fills the voids 210 and is deposited to a thickness beyond the top surface 208 of the first mandrel structures 202. In one embodiment, a suitable apparatus for performing the gap fill deposition process is the PRODUCER® ETERNA™ FCVD™ apparatus available from Applied Materials, Inc., Santa Clara, Calif. It is contemplated that suitably configured apparatus from other manufacturers may also be utilized in accordance with the embodiments described herein.

In one embodiment, the gap fill material is a flowable material. The flowable material has characteristics of a solid material but also has the ability to “flow,” thus enabling substantially void-free bottom up material deposition. In one embodiment, the gap fill material 302 is deposited by a flowable chemical vapor deposition (CVD) process. In one example, a CVD process is utilized to deposit a flowable silicon oxide containing gap fill material 302. In this embodiment, a silicon oxide material is sequentially deposited, cured, and annealed. In another example, a CVD process is utilized to deposit a silicon nitride gap fill material 302. In this embodiment, a silicon nitride material is sequentially deposited and subjected to a nitridation plasma treatment. In another embodiment, the gap fill material 302 is formed by a spin on glass (SOG) process. In this embodiment, the gap fill material 302 is an oxide containing material, such as silicon dioxide and the like.

At operation 740, the gap fill material is planarized. FIG. 4 illustrates a partial cross-sectional view of the substrate 102 of FIG. 3 after planarization of the gap fill material 302 according to an embodiment described herein. In one embodiment, planarization of the gap fill material 302 is performed by an oxide or nitride chemical mechanical polishing process. In another embodiment, planarization of the gap fill material 302 is performed by an oxide or nitride dry etching process or a wet etching process.

The gap fill material 302 is removed to a point where a top surface 402 of the gap fill material 302 is substantially planar with the top surface 208 of the first mandrel structures 202. In one embodiment, it is contemplated that the first mandrel structures 202 are utilized as removal point. In another embodiment, the gap fill material 302 is subjected to a time based process to planarize the surfaces 402, 208.

At operation 750, the first mandrel structures 202 are removed to form the second mandrel structures 500 which include the hardmask material 104 and the gap fill material 302. FIG. 5 illustrates a partial cross-sectional view of the substrate 102 of FIG. 4 with the first mandrel structures 202 removed to form second mandrel structures 500 according to an embodiment described herein. A selective etching process is utilized to remove the first mandrel structures 202. For example, etch chemistries selective to III-V materials are utilized to remove the first mandrel structures 202 preferentially to the oxide and/or nitride containing gap fill material 302 and hardmask material 104.

In one embodiment, a chlorine containing precursor, such as HCl, is delivered to a process environment with a hydrogen containing precursor, such as H₂. The precursors are delivered to the process environment with an inert carrier gas such as N₂ or Ar. In one example, the HCl is delivered to the process environment at a flow rate of between about 1 sccm and about 500 sccm. A temperature of the process environment is maintained between about 300° C. and about 700° C. and a pressure of the process environment is maintained between about 0 Torr and about 100 Torr.

Removal of the first mandrel structures 202 results in spaces 502 formed between adjacent second mandrel structures 500. The spaces 502 also expose the top surface 206 of the substrate 102 which is etched in subsequent processes. A height of the second mandrel structures 500 is similar to the distance 204. It is believed that by utilizing sufficiently thick mandrel structures as masks, subsequent etching processes exhibit improved verticality.

At operation 760, the substrate 102 is etched using the second mandrel structures 500 as a mask to form fin structures 602. FIG. 6 illustrates a partial cross-sectional view of the substrate 102 of FIG. 5 after etching of the substrate 102 according to an embodiment described herein. The etching process is selective for silicon materials and preferentially etches the substrate 102 relative to the oxide and nitride materials of the hardmask material 104 and the gap fill material 302.

In one embodiment, a halogen containing precursor, such as HBr or Cl2 is activated into a plasma and delivered to a process environment with an inert carrier gas, such as Ar. In certain embodiments, oxygen and/or nitrogen containing precursors, such as O₂ or N₂, are also delivered to the process environment. In this embodiment, the precursors are activated by an inductively coupled plasma process with a source power of between about 500 W and about 2000 W and a bias power of between about 50 W and about 500 W. A pressure of the process environment during plasma formation and etching of the substrate 102 is between about 5 mTorr and about 15 mTorr

In one embodiment, etching the substrate 102 utilizes an anisotropic etching process to obtain substantially vertical sidewalls of the fin structures 602. The etching process also forms trenches 604 between adjacent fin structures 602. After the substrate 102 is etched to a desired depth, a height 606 of the resulting fin structures 602 is greater than about 80 nm, such as between about 100 nm and about 200 nm. Subsequent to the fin structure formation, the second mandrel structures 500 may be removed and subsequent semiconductor fabrication operations may be performed on the substrate 102.

In summation, improved mask formation and etching process flows enable fabrication of advanced semiconductor devices. By reducing spacer material height and by increasing the mask height (i.e. first and second mandrel structures), improved etching verticality is achieved. It is also believed that utilizing the process flows described herein, sidewall verticality of the masks (first and second mandrel structures) are improved, which results in desirable etching verticality characteristics. Accordingly, sidewall (lateral growth) is more effectively controlled and edge roughness is also reduced.

While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

What is claimed is:
 1. A fin structure processing method, comprising: forming a patterned hardmask material on a substrate; forming first mandrel structures on regions of the substrate exposed between the patterned hardmask material; depositing a gap fill material on the substrate over the hardmask material and the first mandrel structures; removing the first mandrel structures to form second mandrel structures comprising the hardmask material and the gap fill material; and etching the substrate to form trenches using the second mandrel structures as a mask to form fin structures, wherein fin structures are formed between adjacent trenches.
 2. The method of claim 1 further comprising: depositing a spacer material on the hardmask material and patterning the spacer material.
 3. The method of claim 2, wherein the spacer material pattern is transferred to the hardmask material to form the patterned hardmask material.
 4. The method of claim 2, wherein the patterning the spacer material is performed by a self-aligned double patterning process, a self-aligned quadruple patterning process, or a directed self-assembly process.
 5. The method of claim 1 further comprising: planarizing the gap fill material prior to removing the first mandrel structures.
 6. The method of claim 5, wherein the planarizing the gap fill material is performed by a chemical mechanical polishing process.
 7. The method of claim 1, wherein the hardmask material is a silicon oxide material or a silicon nitride material.
 8. The method of claim 1, wherein the forming the first mandrel structures comprises epitaxially depositing a III-V material on the exposed regions of the substrate.
 9. The method of claim 8, wherein the first mandrel structures are formed from a GaAs material.
 10. The method of claim 1, wherein depositing the gap fill material comprises performing a chemical vapor deposition process.
 11. The method of claim 10, wherein the performing chemical vapor deposition process comprises depositing a flowable silicon oxide material or a flowable silicon nitride material.
 12. The method of claim 1, wherein depositing the gap fill material comprises spinning on an oxide containing material.
 13. The method of claim 1, wherein the first mandrel structures extend a first distance above a top surface of the substrate of greater than about 80 nm.
 14. The method of claim 13, wherein the first distance is between about 100 nm and about 200 nm.
 15. The method of claim 13, wherein the second mandrel structures extend a second distance above the top surface of the substrate approximately equal to the first distance.
 16. A fin structure processing method, comprising: forming a hardmask material on a substrate; depositing a spacer material on the hardmask material; patterning the spacer material; transferring the pattern of the spacer material to the hardmask material by etching the hardmask material to expose regions of the substrate; forming first mandrel structures on the exposed regions of the substrate; depositing a gap fill material on the substrate over the hardmask material and the first mandrel structures; removing the first mandrel structures to form second mandrel structures comprising the hardmask material and the gap fill material; and etching the substrate to form trenches using the second mandrel structures as a mask to form fin structures, wherein the fin structures are formed between adjacent trenches.
 17. The method of claim 16, wherein the patterning the spacer material is performed by a self-aligned double patterning process, a self-aligned quadruple patterning process, or a directed self-assembly process.
 18. The method of claim 16, wherein the first mandrel structures comprise a III-V material and extend a first distance above a top surface of the substrate of greater than about 80 nm.
 19. The method of claim 18, wherein the second mandrel structure extend a second distance above the top surface of the substrate approximately equal to the first distance.
 20. A fin structure processing method, comprising: forming a patterned hardmask material on a substrate; forming III-V material first mandrel structures on exposed regions of the substrate, wherein the III-V material first mandrel structures extend a first distance of greater than about 80 nm above a top surface of the substrate; depositing a flowable oxide gap fill material on the substrate over the hardmask material and the III-V material first mandrel structures; removing the III-V material first mandrel structures to form second mandrel structures comprising the hardmask material and the flowable oxide gap fill material, wherein the second mandrel structures extend a second distance above the top surface of the substrate approximately equal to the first distance; etching the substrate to form trenches using the second mandrel structures as a mask to form silicon containing fin structures, wherein the silicon containing fin structures are formed between adjacent trenches; and removing the second mandrel structures. 